Timing of vaccine administration: Canadian Immunization Guide

For health professionals

Last complete chapter revision (see table of updates): May 2017

General Considerations

To provide optimal protection, recommended immunization schedules should be followed as closely as possible. However, it may not always be possible to follow the immunization schedule; for example, people may miss an appointment or may not be available when a vaccination is due. This chapter identifies factors that vaccine providers should consider when it is necessary to administer a vaccine outside the recommended interval.

For information about the routine childhood immunization schedule and recommended immunization schedules for individuals not previously immunized, refer to the Recommended Immunization Schedules in Part 1. For dosing interval recommendations for immunocompromised persons and persons with chronic diseases, refer to the appropriate chapters in Part 3: Vaccinations of Specific Populations.

Delayed Immunization Schedules

One of the most common deviations from the recommended immunization schedule occurs when a person misses an appointment, resulting in a longer than recommended interval between doses of a vaccine. In general, regardless of the time between doses, interruption of a vaccine series does not require restarting the series as delays between doses do not result in a reduction in final antibody concentrations for most multi-dose products. However, maximum protection may not be attained until the complete vaccine series has been administered. Exceptions include:

Cholera and travellers' diarrhea vaccine; refer to Cholera and Enterotoxigenic Escherichia Coli (ETEC) Travellers' Diarrhea Vaccine in Part 4 for recommendations if the primary series of cholera and travellers' diarrhea vaccine is interrupted.
Rabies vaccines for post-exposure prophylaxis; the vaccination schedule should be adhered to as closely as possible and it is essential that all recommended doses of vaccine be administered. If a dose of vaccine is delayed, it should be given as soon as possible and the schedule resumed. If the vaccination schedule has been altered creating doubt about an appropriate immune response, post-vaccination serology should be obtained 7 to 14 days after completing the rabies vaccination series. Refer to Rabies Vaccine in Part 4 for additional information.

Accelerated Immunization Schedules

In exceptional circumstances, such as in the case of unplanned travel or in outbreak situations when multi-dose vaccine series need to be completed as quickly as possible, accelerated immunization schedules can be used. Full immunization can be achieved by providing doses at less than the recommended interval or before the recommended age (see Table 1).

Doses given at less than the recommended interval

When providing vaccine doses at less than the recommended interval, it is important to know the minimum interval between doses in which an adequate immune response will be achieved. For example, the recommended interval between each of the first 3 doses of the childhood immunization series of diphtheria, tetanus, acellular pertussis, and inactivated polio -containing vaccine is 8 weeks. However, if needed, the first 3 doses may be administered at minimum intervals of 4 weeks.

Refer to vaccine-specific chapters in Part 4 for additional information on recommended and minimum dose intervals for vaccine administration.

Doses given before the recommended age

Age recommendations for receipt of vaccines are based on the age at which the risk of disease is highest and for which vaccine safety and efficacy have been demonstrated. When providing vaccine doses at less than the recommended age, it is important to know the minimum age for administering the vaccine, since doses given before the recommended age may lead to a less than optimal immune response. For example, the minimum age for influenza vaccine is 6 months because the vaccine provides poor protection in younger infants.

There may be circumstances in which administering a vaccine a few days before the recommended age may be appropriate to avoid missing an opportunity for vaccination ( for example, administering a vaccine a few days early to a child who reaches the minimum age for the vaccine on the upcoming weekend). However, generally, if a vaccine dose is given before the recommended age, the dose should be repeated on or after the date when the person reaches the age for which the vaccine is recommended. For example, although measles-mumps-rubella (MMR) vaccine may be given as early as 6 months of age, 2 additional doses of measles-containing vaccine must be administered after the child is 12 months old to ensure long lasting immunity to measles.

Refer to vaccine-specific chapters in Part 4 for additional information on recommended and minimum ages for vaccine administration. Refer to Immunization of Travellers chapter in Part 3 for detailed information about accelerated immunization schedules for travel health protection.

Table 1: Minimum age and minimum intervals between vaccine doses in healthy children less than 18 years of age^{Table 1 Footnote 1}^{Table 1 Footnote 2}
Vaccine	Minimum age at first dose	Minimum time until 2^nd dose	Minimum time until 3^rd dose	Minimum time until 4^th dose	Comments
Diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated polio, Haemophilus influenzae type b (DTaP-HB-IPV-Hib) OR Diphtheria, tetanus, acellular pertussis, inactivated polio, Haemophilus influenzae type b (DTaP-IPV-Hib)	6 weeks	4 weeks	4 weeks	6 months after third dose^{Table 1 Footnote a}	Number of doses of Hib-containing vaccine varies by age. Refer to Haemophilus Influenzae Type B Vaccines in Part 4 for additional information. Table 1 Footnote a Return to table 1 footnote a referrer The fourth dose may be given to children less than 12 months of age in certain situations such as travel, but must be re-administered at or after 12 months of age for sustained immunity. Refer to Diphtheria Toxoid in Part 4 for additional information.
Hepatitis A monovalent (HA)	6 months	24 weeks	N/A	N/A	Refer to Hepatitis A Vaccines in Part 4 for additional information.
Hepatitis B monovalent (HB)	Birth	4 weeks (3 dose schedule) OR 16-24 weeks (2 dose schedule^{Table 1 Footnote b})	8 weeks after second dose AND 16 weeks after first dose	N/A	Table 1 Footnote b Return to table 1 footnote b referrer A 2 dose schedule may be used for adolescents 11 to less than 16 years of age; intervals between doses are product-specific. Refer to Hepatitis B Vaccines in Part 4 for additional information.
Human papillomavirus bivalent (HPV2) (females only)	9 years	4 weeks (3 dose schedule) OR 24 weeks (2 dose schedule^{Table 1 Footnote c})	12 weeks after second dose AND 24 weeks after first dose	N/A	Table 1 Footnote c Return to table 1 footnote c referrer A 2 dose schedule may be used for girls 9 to less than 15 years of age. Refer to Human Papillomavirus Vaccines in Part 4 for additional information.
Human papillomavirus nine-valent (HPV9)	9 years	4 weeks (3 dose schedule) OR 24 weeks (2 dose schedule^{Table 1 Footnote d})	12 weeks after second dose AND 24 weeks after first dose	N/A	Table 1 Footnote e Return to table 1 footnote d referrer A 2 dose schedule may be used for adolescents 9 to less than 15 years of age. Refer to Human Papillomavirus Vaccines in Part 4 for additional information.
Influenza	6 months (inactivated)	4 weeks^{Table 1 Footnote e}	N/A	N/A	Table 1 Footnote f Return to table 1 footnote e referrer Children 6 months to less than 9 years of age, receiving seasonal influenza vaccine for the first time require 2 doses. Refer to the most recent NACI statement on Seasonal Influenza for additional information.
Influenza	2 years (live attenuated)	4 weeks^{Table 1 Footnote e}	N/A	N/A
Measles-mumps-rubella (MMR)	12 months^{Table 1 Footnote f}	4 weeks	N/A	N/A	Table 1 Footnote g Return to table 1 footnote f referrer The first dose may be given at 6 to 12 months of age in certain situations such as travel, but must be re-administered at or after 12 months of age for sustained immunity. Refer to Measles Vaccines in Part 4 for additional information.
Measles-mumps-rubella-varicella (MMRV)	12 months	4 weeks	N/A	N/A	Refer to Measles Vaccines in Part 4 for additional information.
Meningococcal conjugate monovalent serogroup C (Men-C-C)	2 months^{Table 1 Footnote g}	X^{Table 1 Footnote g}	N/A	N/A	Table 1 Footnote h Return to table 1 footnote g referrer The first dose may be given to children less than 12 months of age, but must be re-administered at or after 12 months of age for sustained immunity. For immunization prior to 12 months of age, multiple doses are required; intervals between doses are product-specific. Refer to Meningococcal Vaccines in Part 4 for additional information.
Meningococcal conjugate quadrivalent serogroups A, C, Y, and W-135 (Men-C-ACYW)	N/A	N/A	N/A	N/A	Minimum age for an adolescent dose of (Men-C-ACYW) vaccine has not been determined. Depending on programmatic considerations, the vaccine should be provided according to existing provincial or territorial schedule. Refer to Meningococcal Vaccines in Part 4 for additional information including the minimum age for children in high risk groups.
Pneumococcal conjugate 13-valent (Pneu-C-13)	6 weeks	8 weeks	8 weeks after second dose^{Table 1 Footnote h}	8 weeks after third dose^{Table 1 Footnote h}	Table 1 Footnote i Return to table 1 footnote h referrer Last vaccine dose must be administered at or after 12 months of age. Number of doses may vary depending on age and underlying health condition. Refer to Pneumococcal Vaccines in Part 4 for additional information.
Rotavirus monovalent	6 weeks^{Table 1 Footnote i}	4 weeks^{Table 1 Footnote j}	N/A	N/A	Table 1 Footnote j Return to table 1 footnote i referrer The first dose should be given starting at 6 weeks of age and before 15 weeks of age. Table 1 Footnote k Return to table 1 footnote j referrer All doses should be administered before 8 months of age. Refer to Rotavirus Vaccines in Part 4 for additional information including the maximum age at first dose.
Rotavirus pentavalent	6 weeks^{Table 1 Footnote k}	4 weeks^{Table 1 Footnote l}	4 weeks^{Table 1 Footnote l}	N/A	Table 1 Footnote l Return to table 1 footnote k referrer The first dose should be given starting at 6 weeks of age and before 15 weeks of age. Table 1 Footnote m Return to table 1 footnote l referrer All doses should be administered before 8 months of age. Refer to Rotavirus Vaccines in Part 4 for additional information including the maximum age at first dose.
Tetanus toxoid, reduced diphtheria, reduced acellular pertussis (Tdap)	N/A	N/A	N/A	N/A	Depending on programmatic considerations, the vaccine should be provided according to existing provincial or territorial schedule. Refer to Tetanus Toxoid in Part 4 for additional information.
Varicella (monovalent)	12 months	4 weeks	N/A	N/A	Refer to Varicella (chickenpox) Vaccines in Part 4 for additional information.
Table 1 Footnotes Table 1 Footnote 1 Vaccines provided at less than the recommended age and/or interval should be provided in exceptional circumstances only. Refer to Recommended Immunization Schedules in Part 1 for information about the recommended age at first dose and recommended schedules. Return to table 1 footnote 1 referrer Table 1 Footnote 2 The minimum age and minimum intervals contained in this table are applicable to the immunization of healthy children under 18 years of age using routinely recommended vaccines. Recommendations for persons with underlying medical conditions or in special circumstances may vary from the recommendations included in the table. Refer to Part 4 for vaccine-specific chapters and to Part 3 for condition-specific recommendations. Return to table 1 footnote 2 referrer Abbreviation: Hib: Haemophilus influenzae type b

Concurrent Administration of Vaccines

With consideration of the minimum age and interval between doses, most routine vaccines can be safely and effectively administered at the same visit. When a person is delayed in their immunization schedule, administration of multiple vaccines at the same visit is a strategy for ensuring catch-up immunization. In general, all vaccine doses for which a person is eligible should be administered at a single visit to increase the probability that the individual will be fully immunized. Administration of multiple vaccines is particularly important for people preparing for travel or if it is uncertain that the person will return for additional immunization. Refer to Vaccine Administration Practices in Part 1 for additional information about administration of multiple injections.

Inactivated vaccines

In general, inactivated vaccines may be administered concomitantly with, or at any time before or after, other inactivated vaccines or live vaccines. Exceptions include different formulations of vaccine that protect against the same disease, which should be administered at different visits (for example, pneumococcal conjugate and pneumococcal polysaccharide vaccines).Different injection sites and separate needles and syringes should be used for concomitant parenteral injections. Refer to vaccine-specific chapters in Part 4 for additional information.

Live vaccines

Live vaccines given by the parenteral route may be administered concomitantly with other vaccines during the same visit, using different injection sites and separate needles and syringes. In general, if two live parenteral vaccines are not administered concomitantly, there should be a period of at least 4 weeks before the second live parenteral vaccine is given. When two live parenteral vaccines are given less than 4 weeks apart, the immune response to the second vaccine may be diminished by the immune response to the first vaccine. In these cases, the dose of the second vaccine is considered invalid and should be repeated after the recommended interval. An exception to this rule are varicella-containing vaccines which should not be administered concomitantly with smallpox vaccine. If there is a requirement for both vaccines, the varicella-containing vaccine should be administered at least 4 weeks before or after smallpox vaccine. Refer to Varicella (Chickenpox) Vaccines and Smallpox and Mpox (Monkeypox) Vaccines in Part 4 for additional information.

Live oral vaccines or live intranasal vaccine can be given concomitantly with, or any time before or after any other live or inactivated vaccine, regardless of the route of administration of the other vaccine. Exceptions include oral cholera vaccine (inactivated) and oral typhoid vaccine (live), which should be administered at least 8 hours apart.

Refer to Blood Products, Human Immune Globulin and Timing of Immunization in Part 1 for guidelines for the interval between administration of immune globulin preparations or other blood products and measles-mumps-rubella (MMR), measles-mumps-rubella-varicella (MMRV) or monovalent varicella vaccine vaccines.

Selected references

American Academy of Pediatrics. In: Pickering LK, Baker CJ, Kimberlin DW, et al. (editors). Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012.
Centers for Disease Control and Prevention. Health Information for International Travel 2014. The Yellow Book. Accessed June 2015.
Centers for Disease Control and Prevention. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 2011;60(RR-2):1-61.
Centers for Disease Control and Prevention. Yellow fever vaccine: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2002. MMWR Morb Mortal Wkly Rep 2002; 51(RR-17):1-10.
Centers for Disease Control and Prevention. Typhoid immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 1994;43(RR-14):1-7.
DeStefano F, Goodman RA, Noble GR et al. Simultaneous administration of influenza and pneumococcal vaccines. JAMA 1982; 247(18):2551-54.
Halperin S, McDonald J, Samson L et al. Simultaneous administration of meningococcal C conjugate vaccine and diphtheria-tetanus-acellular pertussis-inactivated poliovirus-Haemophilus influenzae type b conjugate vaccine in children: a randomized double-blind study. Clin Invest Med 2002;25(6):243-51.
King GE, Hadler SC. Simultaneous administration of childhood vaccines: an important public health policy that is safe and efficacious. Pediatr Infect Dis J 1994;13(5):394-407.
Yvonnet B, Coursaget P, Deubel V et al. Simultaneous administration of hepatitis B and yellow fever vaccines. Journal of Medical Virology 1986;19(4):307-11.

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Date modified:: 2023-10-03

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